A Government plan to integrate health and social care is failing to save money or stem the rise in hospital admissions, a report has warned.
The National Audit Office (NAO) said the Department of Health and NHS England were both over-optimistic about what the Better Care Fund for England could achieve.
It was set up with £5.3 billion of NHS and local authority funding in 2015 to better integrate health and social care.
The NHS is suffering due to record-high numbers of delayed discharges, where patients are medically fit to leave hospital but there are delays to arranging their social care in the community.
Councils, which arrange and pay for some of the care, are also under huge pressure due to budget cuts.
The NAO report found the Department of Health expected to achieve savings of £511m in the first year of the Better Care Fund, but this was not realised.
It also expected a reduction in hospital admissions, but in fact they increased.
The report said: "Local areas planned to reduce emergency admissions by 106,000, saving £171 million. However, in 2015/16, the number of emergency admissions increased by 87,000 compared with 2014/15, costing a total of £311 million more than planned.
"Furthermore, local areas planned to reduce delayed transfers of care by 293,000 days in total, saving £90 million.
"However, the number of delayed days increased by 185,000 compared with 2014/15, costing a total of £146 million more than planned."
The NAO also said there was "no compelling evidence" to show that integrating services "leads to sustainable financial savings or reduced hospital activity".
And it said the Government has "not yet established a robust evidence base to show that integration leads to better outcomes for patients".
Almost 20 years of initiatives to join up health and social care by successive governments "has not led to system-wide integrated services", the report went on.
It also warned that almost £2 billion set aside to help integrate services had actually been used to plug deficits at NHS trusts.
The report said there were too many assumptions about the impact of integration.
It said: "A key assumption of the fund - that funding could be transferred from the health sector to social care without adverse impact on the NHS - has proved not to be the case because the health service itself is under financial pressure.
"As a result, the fund has not achieved the expected value for money, in terms of savings, outcomes for patients or reduced hospital activity, from the £5.3 billion spent through the fund in 2015/16."
However, the NAO did notice some benefits from the fund, such as 90% of local areas agreeing or strongly agreeing that delivery of their plan had improved joint working.
Amyas Morse, head of the NAO, said: "So far, benefits have fallen far short of plans, despite much effort. It will be important to learn from the over-optimism of such plans when implementing the much larger NHS sustainability and transformation plans."
Labour and Co-operative MP Meg Hillier, chairwoman of the Public Accounts Committee (PAC), said MPs had warned of flaws in the plan two years ago.
"The committee warned that the focus on reducing emergency admissions to hospital without enough investment in community-based services would increase pressure on adult social care services.
"In fact, the number of emergency admissions continues to increase, as does the number of people unable to leave hospital when they are ready to; increasingly because they need homecare or a place in a care home, which are simply unavailable."
She said full integration by 2020 "is nothing but a pipe dream" unless the Government and NHS England fully involve local services.
An NHS England spokeswoman said: "In some senses the NAO report is a statement of the obvious in that the NHS never believed or claimed that cutting hospital budgets to fund social care would by itself save money overall.
"But we agree with the NAO that the Better Care Fund Mark 1 has helped reduce admissions to care homes and increase the number of older people looked after at home.
"The obvious lesson for the next phase of care integration is that joining up local NHS and council services may be worthwhile, but is not by itself a silver bullet solution to wider pressures on health and social care."
A Department of Health spokesman said: "The Better Care Fund is just one element of this Government's programme to integrate health and social care for the first time - and as the report recognises, it has already incentivised local areas to work together better, with nine out of ten places saying their plans are improving services for patients.
"We will build on this for the future in making care even more joined-up."